Golf club head

ABSTRACT

A golf club head of the present invention includes a crown portion, a face portion, and a hosel portion. The crown portion includes a turbulence-promoting portion that extends from a heel side to a toe side and a back side.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a golf club head.

2. Description of the Related Art

To improve the head speed of a golf club head at impact, a measure ofreducing the air resistance to the golf club head has been proposed. Forexample, each of Japanese Patent Laid-Open No. 2013-538666, JapanesePatent Laid-Open No. 2009-000281, and Japanese Utility Model Laid-OpenNo. 60-135153 discloses a golf club head that reduces the air resistanceby forming a plurality of dimples.

Forming dimples has a predetermined effect for reducing the airresistance. However, the air resistance does not decrease in proportionto the area of dimple formation. If air resistance reducing elementssuch as dimples are formed unnecessarily in a wide area, the manufactureof the golf club head may become complicated, or the appearance may bespoiled.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided agolf club head comprising a crown portion, a face portion, and a hoselportion, wherein the crown portion includes a turbulence-promotingportion that extends from a heel side to a toe side and a back side.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a golf club head according to anembodiment of the present invention;

FIG. 2A is a view of the golf club head in FIG. 1 viewed from the upperside;

FIG. 2B is a sectional view taken along a line I-I in FIG. 1;

FIG. 3A is a perspective view showing the section of a crown portiontaken along a line II-II in FIG. 2A;

FIGS. 3B and 3C are views showing other examples of the structure of aturbulence-promoting portion;

FIGS. 4A and 4B are explanatory views of an air resistance; and

FIG. 5 is an explanatory view of another example.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a perspective view of a golf club head 10 according to anembodiment of the present invention. FIG. 2A is a view of the golf clubhead 10 viewed from an upper side. FIG. 2A is a view showing the golfclub head 10 viewed from the upper side in a case where the golf clubhead 10 is grounded according to a predetermined lie angle and apredetermined loft angle.

The golf club head 10 forms a hollow member. The peripheral walls of thegolf club head 10 constitute a face portion 11 that forms a face(striking face), a crown portion 12 that forms the upper portion of thegolf club head 10, a sole portion 13 that forms the bottom portion ofthe golf club head 10, and a side portion 14 that forms the portionbetween the crown portion 12 and the sole portion 13. Aturbulence-promoting portion 16 to be described later is formed on thecrown portion 12 as an air resistance reducing element. The golf clubhead 10 also includes a hosel portion 15 in which a shaft is insertedand fixed.

In FIGS. 1 and 2A, an arrow dl indicates the face-back direction, and anarrow d2 indicates the toe-heel direction. Normally, the face-backdirection is to a target line direction (target direction of a shot).The toe-heel direction can be defined as, for example, the direction toconnect the toe-side end and the heel-side end of the sole portion 13 orthe direction perpendicular to the face-back direction.

The golf club head 10 is a golf club head for a driver. However, thepresent invention is applicable to wood type golf club heads including afairway wood other than drivers, utility (hybrid) golf club heads, andother golf club heads.

The golf club head 10 can be made of a metal material. Examples of themetal material are a titanium-based metal (for example, titanium alloy6A1-4V-Ti), stainless steel, and a copper alloy such as berylliumcopper.

The golf club head 10 can be assembled by joining a plurality of parts.For example, the golf club head 10 can be formed from a body member anda face member. The body member forms the peripheral portions includingthe crown portion 12, the sole portion 13, the side portion 14, thehosel portion 15, and the face portion 11. An opening is formed at partof the portion corresponding to the face portion 11. The face member isjoined to the opening of the body member.

The hosel portion 15 will be described with reference to FIG. 2B inaddition to FIGS. 1 and 2A. FIG. 2B is a sectional view taken along aline I-I in FIG. 1, that is, a sectional view taken along a planeperpendicular to the axis of the hosel portion 15.

In this embodiment, the hosel portion 15 has a cylindrical shape.However, the hosel portion 15 may have another tubular shape such as anelliptic cylindrical shape. A concave portion 15 a is formed in thetoe-side outer surface of the hosel portion 15. In this embodiment, theconcave portion 15 a has a circular shape (spherical shape). However, itmay have a polygonal shape. Since the concave portion 15 a is provided,the separation position of an airflow at impact can be changed to theback side as compared to a case without the concave portion 15 a, andthe air resistance caused by the presence of the hosel portion 15 can bereduced. The concave portion 15 a has a depth of, for example, 0.1 mm to1 mm and a diameter of, for example, 1 mm to 10 mm. The concave portion15 a can be provided, in the outer surface of the hosel portion 15, at aposition within the hosel diameter in the face-back direction withrespect to the toe-side end where the airflow readily separates as thecenter. The toe-side end position is preferable, as in this embodiment.In this embodiment, only one concave portion 15 a is provided. However,a plurality of concave portions may be provided. When providing aplurality of concave portions, the plurality of concave portions can beprovided in a direction parallel to the axial direction of the hoselportion 15, in the face-back direction, or in both directions.

The turbulence-promoting portion 16 will be described with reference toFIG. 3A in addition to FIGS. 1 and 2A. FIG. 3A is a perspective viewshowing the section of the crown portion 12 taken along a line II-II inFIG. 2A.

The turbulence-promoting portion 16 generates small turbulence on thesurface, and suppresses separation of an airflow flowing on the surfaceof the crown portion 12 from the surface of the crown portion 12. Whenthe turbulence-promoting portion 16 is formed at a position whereairflow separation from the crown portion 12 readily occurs, theposition where airflow separation occurs can be moved to the back side.As a result, the air resistance can be reduced.

In FIGS. 1 and 2A, the turbulence-promoting portion 16 is indicated by athick line so that its presence can easily be visually recognized fordescriptive convenience. However, visual recognition of the actualturbulence-promoting portion 16 is impossible or difficult depending onits structure. Conversely, the turbulence-promoting portion 16 may havea visually emphasized structure.

The turbulence-promoting portion 16 extends from the heel side to thetoe side and the back side. The length and the position or area of theturbulence-promoting portion 16 can appropriately be set. If theturbulence-promoting portion 16 is formed over a wide area, themanufacture of the golf club head 10 may become complicated, or theappearance may be spoiled. That is, the turbulence-promoting portion 16is preferably provided in a portion effective for reducing the airresistance.

In this embodiment, the turbulence-promoting portion 16 extends in aline or band shape from the base of the hosel portion 15 to the toe-sideedge of the crown portion 12, and crosses the crown portion 12 obliquelyin the toe-heel direction. When the turbulence-promoting portion 16crosses the crown portion 12 as in this embodiment, an airflow flowingon the surface of the crown portion 12 hardly separates throughout inthe toe-heel direction.

In this embodiment, the turbulence-promoting portion 16 has an outershape that bends a plurality of times. This is because theturbulence-promoting portion 16 is formed following the positions wherethe airflow separates from the crown portion 12. However, the outershape of the turbulence-promoting portion 16 may be simplified to alinear shape or arcuate shape.

In a wood type golf club head having a general shape, airflow separationfrom the crown portion at impact tends to occur relatively from aface-side position on the heel side and from a back-side position on thetoe side. That is, a line that connects the positions where the airflowseparates obliquely crosses the crown portion 12.

The turbulence-promoting portion 16 may be formed such that an angle ebetween the toe-heel direction and a virtual line L1 that connects theheel end and the sole end becomes 5 degrees (inclusive) to 50 degrees(inclusive), depending on the shape of the golf club head, though. Theturbulence-promoting portion 16 is thus located in a region where theairflow separates in a case without the turbulence-promoting portion 16,and the airflow separation position can easily be moved to the backside.

In a wood type golf club head having a general shape, airflow separationfrom the crown portion at impact tends to occur at a position acrossover the top of the crown portion. In this embodiment, theturbulence-promoting portion 16 passes the back side of a top 12 a ofthe crown portion 12. Hence, the turbulence-promoting portion 16 islocated in the region where the airflow separates in a case without theturbulence-promoting portion 16, and the airflow separation position caneasily be moved to the back side. Note that the top 12 a can be definedas the highest position of the crown portion 12 in a case where the golfclub head 10 is grounded according to a predetermined lie angle and apredetermined loft angle.

The turbulence-promoting portion 16 according to this embodiment isformed by roughening the surface of the crown portion 12. Out of thecrown portion 12, a region S1 on the side of the face portion 11 withrespect to the turbulence-promoting portion 16 is smoother than theturbulence-promoting portion 16. The turbulence-promoting portion 16 isthus prevented from being formed over a wide area. In addition, sincethe region S1 of the crown portion 12 on the side of the face portion 11readily comes into golfer's sight upon addressing, it may be possible toreduce strange feeling or improve the appearance by forming a smoothersurface.

In this embodiment, out of the crown portion 12, a region S2 on the backside with respect to the turbulence-promoting portion 16 is alsosmoother than the turbulence-promoting portion 16. Theturbulence-promoting portion 16 is thus prevented from being formedunnecessarily in a wide area. The surface roughness of the region S1 andthat of the region S2 may be equal in design.

As shown in FIG. 3A, the turbulence-promoting portion 16 according tothis embodiment is formed by forming a number of concave portions 16 ain the surface of the crown portion 12. Each concave portion 16 a has acircular shape but may have a square shape. A width W of theturbulence-promoting portion 16 in the face-back direction can make theformation region of the narrow turbulence-promoting portion 16 small.However, if the formation region is too narrow, the turbulence promotingeffect may decrease. Hence, the width W is preferably 2 mm to 30 mm. Thesurface roughness of the turbulence-promoting portion 16 is preferably,for example, 2 μm (inclusive) to 30 μm (inclusive) as an arithmetic meanroughness Ra.

The turbulence-promoting portion 16 can also be formed by a method otherthan the concave portions 16 a. For example, the turbulence-promotingportion 16 can be formed by a plurality of grooves. FIG. 3B shows anexample. In the example of FIG. 3B, a plurality of grooves 16 bextending in the extending direction of the turbulence-promoting portion16 are formed. The turbulence-promoting portion 16 can also be formedby, for example, a plurality of linear convex portions or a number ofpoint-like convex portions. FIG. 3C shows an example. In the example ofFIG. 3C, a plurality of linear convex portions 16 c extending in theextending direction of the turbulence-promoting portion 16 are formed.

Examples of the method of forming the turbulence-promoting portion 16are casting, forging, laser machining, blasting, and milling.

The effect of reducing the air resistance of the hosel portion 15 by theturbulence-promoting portion 16 and the concave portion 15 a will bedescribed next with reference to FIGS. 4A and 4B. FIGS. 4A and 4B areviews schematically showing an airflow acting on the golf club head 10immediately before impact. FIG. 4A shows a case where theturbulence-promoting portion 16 and the concave portion 15 a are absentas a comparative example. FIG. 4B shows this embodiment.

As shown in FIG. 4A, immediately before impact, the airflow to the golfclub head 10 flows in the face-back direction. An airflow flowing on thesurface of the crown portion 12 changes to a laminar flow on the side ofthe face portion 11 and separates halfway. In addition, an airflowflowing on the toe side of the hosel portion 15 separates near thetoe-side end of the outer surface of the hosel portion 15. The earlierthe airflow separates, the larger the air resistance to the golf clubhead 10 is.

In this embodiment shown in FIG. 4B, small turbulence is generated bythe turbulence-promoting portion 16, airflow separation on the crownportion 12 delays, and the separation position shifts to the back side.Additionally, because of the presence of the concave portion 15 a,separation of the airflow flowing on the toe side of the hosel portion15 also delays, and the separation position shifts to the back side. Asa result, the air resistance to the golf club head 10 can be reduced.

As a detailed example, a case where the turbulence-promoting portion 16is formed by the plurality of grooves 16 b, as shown in FIG. 3B, wassimulated on a computer. Note that FIG. 3B shows the grooves 16 b aseasy to recognize, and their scale does not necessarily match the actualscale. Each groove 16 b was a groove having a U-shaped section. Thegroove width was 0.2 mm, the groove depth was 0.02 mm, and the pitchbetween the grooves was 0.4 mm. The width W of the turbulence-promotingportion 16 was 12 mm, and the surface roughness of theturbulence-promoting portion 16 was 5 μm as the arithmetic meanroughness Ra. As a result, a model with the turbulence-promoting portion16 exhibited improvement of the air resistance as compared to a modelwithout the turbulence-promoting portion 16.

To minimize the area of the turbulence-promoting portion 16, theturbulence-promoting portion 16 is provided at the airflow separationposition described with reference to FIG. 4A.

The position of the turbulence-promoting portion 16 can be determined bya simulation on a computer. That is, the airflow at impact is simulatedfor a prototype of a golf club head without the turbulence-promotingportion 16, and portions of the crown portion 12 where the airflowseparates are specified. The turbulence-promoting portion 16 is thendesigned so as to follow and include the specified portions. A golf clubhead including the turbulence-promoting portion 16 is thus manufactured.This makes it possible to more easily reduce the air resistance to thegolf club head without forming the turbulence-promoting portion 16 overa wide area.

Other Embodiments

In the above-described embodiment, only one turbulence-promoting portion16 is provided. However, a plurality of turbulence-promoting portions 16may be formed. FIG. 5 shows an example. In the example of FIG. 5, aturbulence-promoting portion 16A and a turbulence-promoting portion 16Bthat are spaced apart in the face-back direction are formed. Althoughtwo turbulence-promoting portions are formed here, three or moreturbulence-promoting portions may be provided. However, the number ispreferably two from the viewpoint of preventing the turbulence-promotingportions from unnecessarily increasing.

The turbulence-promoting portion 16A is the same as the above-describedturbulence-promoting portion 16. The turbulence-promoting portion 16Bcan have the same structure as the above-described turbulence-promotingportion 16. However, the position is different, and theturbulence-promoting portion 16B is formed on the back side with respectto the turbulence-promoting portion 16A. If improvement of theseparation position by the turbulence-promoting portion 16A isinsufficient, the turbulence-promoting portion 16B can be provided at aportion where the airflow separates relatively early. When theturbulence-promoting portion 16B is provided, the airflow separationposition on the crown portion 12 can further be shifted to the backside, and the air resistance can be reduced.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2014-250300, filed Dec. 10, 2014 which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A golf club head comprising a crown portion, aface portion, and a hosel portion, wherein said crown portion includes aturbulence-promoting portion that extends from a heel side to a toe sideand a back side.
 2. The golf club head according to claim 1, wherein aregion of said crown portion on a side of said face portion with respectto said turbulence-promoting portion is smoother than saidturbulence-promoting portion.
 3. The golf club head according to claim1, wherein said crown portion includes at least one otherturbulence-promoting portion on the back side with respect to saidturbulence-promoting portion.
 4. The golf club head according to claim1, wherein said turbulence-promoting portion extends in one of a lineshape or a band shape.
 5. The golf club head according to claim 1,wherein an arithmetic mean roughness Ra of said turbulence-promotingportion is 2 μm (inclusive) to 30 μm (inclusive).
 6. The golf club headaccording to claim 1, wherein a concave portion is formed in an outersurface of said hosel portion on the toe side.
 7. The golf club headaccording to claim 1, wherein an angle between a toe-heel direction anda virtual line that connects a heel end and a sole end of saidturbulence-promoting portion is 5 degrees (inclusive) to 50 degrees(inclusive).
 8. The golf club head according to claim 1, wherein aregion of said crown portion on the back side with respect to saidturbulence-promoting portion is smoother than said turbulence-promotingportion.
 9. The golf club head according to claim 1, wherein saidturbulence-promoting portion extends from a base portion of said hoselportion to a toe-side circumferential edge of said crown portion. 10.The golf club head according to claim 1, wherein saidturbulence-promoting portion passes the back side of a top of said crownportion.